Final answer:
P&ID symbols represent equipment and tanks used in process systems, such as a nuclear power plant's containment shell, control rods, reactor, water pump, steam generator, and electric output.
Step-by-step explanation:
The symbols in the main drawing of a P&ID (Piping and Instrumentation Diagram) represent pieces of equipment and tanks. These diagrams are essential in the design, operation, and maintenance of process systems, including those in nuclear power plants. A P&ID shows the piping, including the physical sequence of branches, reducers, valves, equipment, instrumentation and control interlocks. For example, a diagram of a nuclear power plant might include symbols representing the containment shell, control rods, reactor, water pump, steam generator, and electric output. Each symbol is a simplified representation of the component's role in the process system, allowing for a clear and concise overview of how the system functions.